The Wuxi Marathon in March 2024 is a battle for many runners. The temperature of the day was 14°C and the humidity was 95%. After 9 o'clock, the temperature did not exceed 20°C, but the humidity remained high. It can be seen that humidity has a great impact on running.

In the Guangzhou Marathon in December 2023, the temperature reached 25-26°C on the day of the race, and the humidity was as high as 90%. The medical team of the First Hospital of Sun Yat-sen treated a total of 2,321 participants, including 2,148 with muscle spasms and 62 with dehydration. The official rabbit 300 crashed three, the 330 collapsed two, the 430 also collapsed, the 600 collapsed two, and the blacks also got on the containment vehicle!

01 The suitable temperature for running is 4-20°C:

When the temperature is too low, blood vessels will constrict, muscles will become stiff, and joints will become less flexible. At this time, running is more likely to induce respiratory diseases.

The temperature is too high, and at the same time, there is a lot of perspiration, and the convection effect of body temperature and temperature is poor, which is not conducive to body heat dissipation.

02 The suitable humidity for running is 50-60%:

If the humidity is too low, the air will rob the body of moisture, and the evaporation of water on the body surface will be accelerated, resulting in dry skin.

Too much humidity is not conducive to sweat glands, causing heat to remain in the body, and as the core body temperature rises during running, nausea and other phenomena begin to occur.

The best representative of the low temperature and high humidity environment is the winter in Jiangsu, Zhejiang and Shanghai - the clothes feel wet and can never be dried, the temperature shows a few degrees above zero but feels extremely cold and biting, and the amount of sweat after running is a lot, if you don't keep warm and change clothes in time after running, you are particularly prone to cold.

03 Effect of temperature & humidity on pace

For the mass runners participating in the marathon, they also need to adjust the pace strategy accordingly according to the humidity & temperature conditions at the race site, otherwise it is easy to crash (elite runners are more resistant to beating, and the adjustment value will be smaller than in the table).

Effect of temperature & humidity on pace (individual differences for reference)

04 Perceived temperaturePerceived temperature is the temperature of the air felt by the human body, which may be quite different from the temperature in the usual weather forecast.

For example, I often hear that the winter in Jiangsu, Zhejiang and Shanghai freezes into a dog, which is far less warm than in the north; African students can't survive the summer in Wuhan and Hangzhou, which is a reflection of the temperature they feel. 

The perceived temperature is mainly related to relative humidity, wind, air temperature, and sunlight intensity, and only when these data are in a certain range, it is a good day to race. Generally speaking, the best perceived temperature of the human body is about 20-25 °C (in winter, the human body can accept 18~23 °C. 25-26°C in summer).

Figure: Difference in perceived temperature under different air temperatures & humidity

Perceived Temperature Heat Index The darker the color block, the more vigilant you need to be

Source: National Oceanic and Atmospheric Administration (NOAA)

The most suitable marathon temperature is about 6~8 °C, within 10-15 °C is good, more than 15 °C is actually quite hot, more than 20 °C, the race performance will drop significantly.

Tips | How to run safely in hot summer weather?

1. Check the humidity and temperature before running

2. Replenish water and electrolytes in time

15 minutes before running, you can start with a glass of water. Drink at least half a glass of water or electrolyte water every 15 minutes during the run (to avoid electrolyte imbalance in the body).

3. Wear moisture-absorbing and sweat-wicking clothes, preferably light-colored.

4. Sunscreen

It's best to wear a hat, sunglasses, and sunscreen.

5. Avoid extreme heat periods

Between 10 a.m. and 5 p.m. is the hottest time of the day, and running should be avoided during this time period.

6. Adjust the training plan

Experienced runners are sometimes controlled by plans or data, and at this time, they actually need to adjust their training plans, and temperature and humidity are also one of the variable factors in the training plan.

7. Adjust the running route

Prioritize routes with plenty of shade, or where you can buy water in time to ensure you're hydrated and cool while running.

8. Run with friends

Running with friends allows you to observe and monitor each other's situation, and when someone feels unwell, the other person can help him adjust in time.

9. Choose an indoor workout

The indoor gym is air-conditioned and is the best place to work out in the hot summer weather. In addition to satisfying the needs of running, you can also do strength or other training, and exercising in the gym is also a good way to improve the overall quality of the body.

In short, slow down!